{ "background": "Maintenance depot systems are critical for the reliability of transport infrastructure, yet their performance in sub-Saharan contexts is under-studied. Current evaluations often rely on retrospective, non-experimental data, limiting causal inference on system efficacy.", "purpose and objectives": "This study aimed to implement and evaluate a novel randomised field trial methodology to measure the operational reliability of road maintenance depot systems, with the objective of generating robust, experimental evidence on causal factors affecting depot performance.", "methodology": "A randomised controlled trial was conducted across a network of depots. Depots were randomly assigned to an intervention group receiving enhanced logistical protocols or a control group maintaining standard practice. System reliability was measured as the time-to-failure of depot output against specified performance thresholds. The primary analysis used a Cox proportional hazards model: $h(t|X) = h0(t) \\exp(\\beta1 X1 + \\beta2 X2)$, where $X1$ represents the intervention and $X_2$ a depot size covariate.", "findings": "Depots in the intervention group demonstrated a 40% lower hazard of performance failure compared to control depots (hazard ratio = 0.60, 95% CI: 0.48 to 0.75). The median time-to-failure increased from 42 days to 68 days under the enhanced protocol. Uncertainty was quantified using robust standard errors clustered at the regional level.", "conclusion": "The randomised field trial proved a viable method for rigorous, causal evaluation of engineering maintenance systems in this context. The intervention significantly enhanced depot reliability.", "recommendations": "Transport authorities should adopt principles of experimental design for system evaluations. The specific logistical protocols tested here warrant broader implementation and scaling.", "key words": "infrastructure maintenance, randomised controlled trial, system reliability, transport engineering, field experiment", "contribution statement": "This paper provides the first application of a randomised field trial to evaluate transport maintenance depot systems in sub